The present invention relates generally to a display panel filter, and more particularly to a filter having particular application for use with a plasma display panel or flat panel display. The present invention also relates to an IR/EMI filter film applied to a substrate for use in a display panel filter or otherwise and a method of making such a film and a display panel filter.
Visual display panels commonly known as plasma display panels or flat panel displays have been recently introduced for the purpose of displaying visual images or information on relatively large, flat screens. Plasma display panel technology utilizes selectively energized gas ions to bombard phosphors on a display screen, similar to an electron beam bombarding phosphors on a cathode ray tube (CRT) screen. Plasma display panels are similar to CRT displays in that both provide a means for visually displaying information or images from an input signal; however, important differences exist. First, a CRT display requires a significant depth dimension relative to the size of its display screen to accommodate a generally funnel shaped rearward portion for generation and deflection of the electron beam. Second, most CRT screens are curved. In contrast, the energization of the ions in a display panel using plasma display technology occurs in a relatively thin vacuum chamber adjacent to the display screen, resulting in a relatively thin display panel with a flat view face. Thus, plasma display panels are currently used primarily for relatively large display panels where CRTs are impractical or where a display panel with a significantly reduced depth dimension is necessary or desirable.
Although plasma display panels provide significant advantages and improvements by facilitating relatively large visual displays with a reduced panel depth and by otherwise facilitating the use of displays in environments with space restrictions which preclude the use of conventional CRT displays, new problems have arisen. These problems relate to the quality of the visual display, increased infrared (IR) and electromagnetic interference (EMI) emissions, low contrast ratio and consumer safety issues. For example, photopic reflection from many plasma display panels is in excess of 15%. This adversely affects the quality of the display. Further, operation of the plasma display panel produces or has the potential of producing infrared (IR) emissions which are capable in some cases of interfering with a remote control of the panel or other devices utilizing infrared signaling. Still further, operation of the plasma display panel results in the generation and emission of electromagnetic interference (EMI). Accordingly, many plasma panel displays fail to meet governmental TCO and FCC requirements for EMI emissions and the stricter standards for various military, aircraft and other uses. The above problems necessary limit the applicability and desirability of using plasma display panels.
Accordingly, there is a critical need in the art for a device or a filter, and in particular a multi-layer filter film, useable in conjunction with plasma display panels for addressing and solving the above problems and limitations. A need also exists for a method of making such a device, filter or film.
To satisfy the need in the art, the present invention provides a device in the form of a single filter which is useable in conjunction with plasma display panels or other applications and which functions to reduce reflection after assembly to acceptable levels, to increase contrast enhancement, to maintain transmission integrity, to assist in reducing EMI emissions to levels which comply not only with consumer safety regulations, but with the stricter military and aircraft standards, and to reduce infrared emissions in the 800 nm-1000 nm range to a level which does not interfere with remote control operation.
Generally, the present invention comprises a substrate with a filter film (preferably an IR/EMI shielding film) applied thereto for use in a display panel filter. One embodiment of a filter device in accordance with the invention includes a filter film comprised of one or more conductive layers and one or more dielectric layers applied to a substrate which is then laminated to a second substrate. This second substrate may comprise a piece of transparent glass, plastic or other material, a flexible film such as PET film or the front face of the display device itself. The combination of the conductive and dielectric layers functions to provide the desired EMI and IR shielding and assists in reducing reflection and increasing contrast enhancement. This combination of layers may be provided as a single film containing both conductive and dielectric layers. Because lamination of the substrates necessarily requires use of an adhesive or other bonding agent and exposure of the same to at least one surface of the shielding film or filter, a layer of silicon dioxide (SiO2) or other material may be applied to the filter or film, if desired, to improve compatibility with and/or limit possible reactions between the outer layer of the filter or film and the adhesive. The outer surfaces of one or both substrates is also preferably an anti-reflective (AR) coating. The filter further includes an electrical connection member electrically connected to conductive layers within the EMI/IR shielding film. Grounding means is also provided in the form of an electrical wire or the like for electrically connecting the electrical connection member to a grounded terminal. Other means, however, may also be utilized.
The preferred embodiment of the shielding film comprises one or more layers of a conductive material and one or more alternating layers of a dielectric. The conductive material may include various conductive metals or other materials such as silver, copper, gold and indium tin oxide, among others, although silver metal is preferred. The dielectric may include various materials such as niobium pentoxide, titanium dioxide and tin oxide, among others, although niobium pentoxide is preferred. Additionally, a thin protective layer is provided between adjacent conductive/dielectric layers to eliminate or limit undesirable oxidation or other deterioration of the conductive layer during formation of the film or otherwise. Such a protective layer is desirable when the conductive layer is subject to oxidation or other deterioration and/or the manufacturing conditions result in the film being exposed to high temperatures. Such conditions exist when the film is manufactured using sputtering or various other thin film deposition techniques, particularly for multiple layer films of two or more conductive material layers. In some cases, the protective layer is comprised of two or more layers of different materials.
In the preferred embodiment, the transparent substrates comprise view side and panel side substrates with the panel side substrate being the substrate closest to, or adjacent to, the display screen. Similarly, each of the substrates includes a view side facing away from the display screen and a panel side facing the display screen. In the preferred embodiment, the EMI/IR shielding film or filter is applied directly to the view side of the panel side substrate and the two substrates are laminated together by a urethane or other adhesive. The preferred embodiment further includes an environmental degradation barrier for the conductive layers within the EMI/IR shielding layer. This barrier extends around the edge of the laminated filter and is constructed of a conductive material. This barrier is electrically connected both with the electrical connection member or busbar and with a grounding terminal.
The method aspect of the present invention relates to a method of making a film or filter of the type described above for use in conjunction with a plasma display panel. Such method generally includes providing a transparent substrate, applying an EMI/IR shielding film or filter to such substrate and then laminating such substrate to a second substrate.
Accordingly, an object of present invention is to provide a film or filter for use in conjunction with a plasma display panel.
Another object of the present invention is to provide a plasma display panel filter which provides anti-reflective, EMI shielding, contrast enhancement and infrared shielding capabilities and which also complies with consumer safety requirements.
A further object of the present invention is to provide a plasma display panel filter having one or more conductive layers and one or more dielectric layers formed on a transparent substrate for subsequent lamination to a second substrate.
A still further object of the present invention is to provide a plasma display panel filter with an improved film providing both EMI and IR shielding capabilities.
A further object of the present invention is to provide a plasma display panel filter with an improved means for electrically connecting the EMI shielding layer to a grounding terminal.
A still further object of the present invention is to provide a plasma display panel filter with an electrically conductive material around the edge of the filter to prevent environmental degradation of the EMI shielding layer and to maximize the EMI shielding efficiency of such layer.
A still further object of the present invention is to provide a plasma display panel as described above which includes a layer to prevent or minimize possible reactions between the lamination adhesive and the shielding film and/or to improve compatibility with the adhesive and promote the adhesive strength.
Another object of the present invention is to provide a method of making a film and plasma display panel filter of the type described above.
These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and method and the appended claims.